Experimental measurements of the permeability characteristics of rare earth ore under the hydro-chemical coupling effect

Abstract

Two coupling processes—solution seepage and chemical replacement—occur in the in situ leaching process of ion-absorbed-rare-earth ore. In this study, saturated leaching tests were applied to investigate the permeability characteristics of rare earth ore under the hydro-chemical coupling effect. The pore radius distributions based on two leaching solutions (H₂O and (NH₄)₂SO₄) were obtained by nuclear magnetic resonance detection technology. The results indicated that 10–25 μm and 4–10 μm pores are dominant in the ore under solution leaching using H₂O and (NH₄)₂SO₄, respectively. A “black belt” in the pores of (NH₄)₂SO₄ leaching was discovered from the reconstruction of the pore structure distribution image. The results also reveal that the hydraulic conductivity will initially increase, then decrease and finally increase during the leaching process. The hydro-chemical coupling effect will lead to variations in the pore structure and permeability of rare earth ore. The pore radius will increase due to solution seepage, whereas it decreases due to the particle recombination induced by chemical replacement. The permeability of rare earth ore is influenced more by chemical replacement than by solution seepage.